1. Field of the Invention
This invention relates to a data reproducing device for reproducing music data and image data which are recorded on a data carrier.
2. Description of the Prior Art
As shown in the signal format illustrated in FIG. 3, in addition to music data, a series of digital data called "sub-codes" are recorded on a compact disc in which music data are recorded in the form of digital data. Each sub-code is made up of eight (8) bits. Of the eight bits, two higher-order bits correspond to a P signal and a Q signal, and the remaining six bits are used as image data. The sub-code is so determined that ninety-eight image words correspond to one frame of the sub-code. The P signal indicates the top of a piece of music, and it is raised to "1" at the top of the piece of music and held at "0" at the other positions. The Q signals are used to record a music number, data concerning the length of time for a piece of music (hereinafter referred to as "music time lapse data", when applicable), and data concerning the total time from the start (hereinafter referred to as "total time data", when applicable).
For the image data, ninety-eight words each consisting of six bits are provided as shown in FIG. 4(A). Of the ninety-eight words, the first and second are used as a synchronizing signal, and the remaining words are used as image data. The ninety-six words of image data are made up of four groups of unitary image data in which twenty-four words is a minimum unit.
In the unitary image data, as shown in FIG. 4(B), the record mode is recorded in the first word an image processing instruction is recorded in the second word, and error correction signs for the first and second words are recorded in the third and fourth words.
As for the record mode, a line graphics mode and a TV graphics mode are provided. As for the image processing instruction, an instruction for covering a screen with a color, an instruction for applying two different colors to a screen forming units (fonts) to draw a figure, an instruction for moving an entire screen vertically or horizontally, and so forth are available.
A channel number and color data for specifying picture color are recorded in the fifth and sixth words. Position data for indicating a data display position in the picture are recorded in the seventh and eight words, and data and error correction signs are recorded in the last sixteen words (i.e., the ninth through twenty-fourth words).
FIG. 5 is a block diagram showing a conventional data reproducing device for playing a disc in which music data and image data including sub-codes have been recorded.
The data reproducing device, as shown in FIG. 5, comprises; a player 1; a sound generating unit 2 including an amplifier and a loudspeaker: a display unit 3; and a data processing unit 4. The player 1 reads music data, sub-codes, etc. from the disc D to apply a reproduction signal to the data processing unit 4. The unit 4 extracts the music data and image data from the output reproduction signal of the player 1, to control the sound generating unit 2 and the display unit 3.
The output reproduction signal of the player 5 is first applied to a decoder 5 in the data processing unit 4, where it is subjected to deinterleaving and error correction, and the music data is applied through a processing circuit (not shown) to the sound generating unit 2 while the image data is applied to an instruction discriminating circuit 6. The instruction discriminating circuit 6 determines whether or not an image processing instruction is recorded in the second word (FIG. 4(B)) of the sub-code and outputs a detection signal when an image processing instruction is present. An instruction analyzing circuit 7 operates to analyze an image processing instruction, to thereby provide data which specify the colors of the picture elements of the picture according to the image data recorded in the sub-code. In response to the output data of the instruction analyzing circuit 7 and the output detection signal of the instruction discriminating circuit 6, a display control circuit 8 forms video signals including color signals and synchronizing signals, so that the image data is displayed on the display unit 3.
In the case where, with the conventional data reproducing device, the music data recorded in the disc D is manually searched with the player 1 by fast forwarding or fast reversing, the player 1 performs a sequential operation where data at discontinuous parts of the disc D are reproduced sequentially. As for the music data, even when sound reproduction is made with data obtained from separate parts of the disc, we hear it naturally. On the other hand, the image data recorded in the sub-code is a sequential data train. Therefore, if a discontinuous reproduction is produced, for instance, by manual search, the continuity of the image data is lost. As a result, the displayed picture is missing parts over the entire screen, suffers from double writing, or is abnormal in coloration. That is, the reproduction is unsatisfactory. Thus, the conventional data reproducing device is unreliable, and the user may find the resultant picture disagreeable.